diff --git a/esphome/components/api/proto.h b/esphome/components/api/proto.h
index cf03f48be8..702208d9de 100644
--- a/esphome/components/api/proto.h
+++ b/esphome/components/api/proto.h
@@ -468,7 +468,8 @@ class ProtoMessage {
   virtual const char *message_name() const { return "unknown"; }
 #endif
 
-  // Non-virtual: messages are never deleted polymorphically.
+ protected:
+  // Non-virtual destructor is protected to prevent polymorphic deletion.
   ~ProtoMessage() = default;
 };
 
diff --git a/script/api_protobuf/api_protobuf.py b/script/api_protobuf/api_protobuf.py
index b00cbab37a..85352689e6 100755
--- a/script/api_protobuf/api_protobuf.py
+++ b/script/api_protobuf/api_protobuf.py
@@ -280,6 +280,9 @@ class TypeInfo(ABC):
         """
         field_id_size = self.calculate_field_id_size()
         method = f"calc_{base_method}_force" if force else f"calc_{base_method}"
+        # calc_bool_force only takes field_id_size (no value needed - bool is always 1 byte)
+        if base_method == "bool" and force:
+            return f"size += ProtoSize::{method}({field_id_size});"
         value = value_expr or name
         return f"size += ProtoSize::{method}({field_id_size}, {value});"